- #1
jeneekim
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Homework Statement
An electric motor can accelerate a Ferris
wheel of moment of inertia 11300 kg · m2 from
rest to 9.6 rev/min in 14.6 s. When the mo-
tor is turned off, friction causes the wheel to
slow down from 9.6 rev/min to 8.37 rev/min
in 7.23 s.
Determine the torque generated by the mo-
tor to bring the wheel to 9.6 rev/min.
Answer in units of N · m.
Homework Equations
[tex]\alpha[/tex] = [tex]\omega[/tex]/t
[tex]\tau[/tex] = I[tex]\alpha[/tex]
The Attempt at a Solution
given:
I = 11300 kgm2
[tex]\omega[/tex]o = 0
[tex]\omega[/tex]f = 9.6 rev/min = 1.005309649 rad/s
tf = 14.6 s
The question asks to determine the torque generated by the motor to bring the wheel to 9.6 rev/min so I think that means I don't have to worry about the motor beign turned off or the friction to slow it down... sooooo...
[tex]\alpha[/tex] = [tex]\omega[/tex]/t
= (1.005309649 rad/s)/(14.6s)
= 0.0688568253 rad/s2
[tex]\tau[/tex] = I[tex]\alpha[/tex]
= (11300kgm2)(0.0688568253 rad/s2)
= 778.0821257 Nm
When I enter this answer, it says it is wrong? What am I doing wrong here?
Thank you in advance for your help!
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